1. Field of the Invention
The present invention relates to a transmission electron microscope provided with an electronic spectroscope which spectrally decomposes an electron beam by an amount of energy which the electron beam has and, more particularly, relates to a transmission electron microscope which makes a convergent position differ in an energy dispersion direction of an electronic spectroscope and a direction perpendicular to the energy dispersion direction. Furthermore, the present invention relates to a method for correcting magnification or position that can perform correction of magnification or correction of measurement position of a spectral image acquired by the transmission electron microscope with high efficiency and high accuracy, and relates to a correction system for achieving the correction method.
2. Description of the Related Art
Processing dimensions of a silicon semiconductor, a magnetic device, and the like have been becoming minute and their high integration has been being achieved; and deterioration of device characteristics and degradation of reliability have been further becoming important problems. In recent years, a spectral analysis and a two-dimensional element distribution analysis using a (scanning) transmission electron microscope ((S) TEM) and an electron energy loss spectroscopy (EELS) have been becoming indispensable analysis means in order to analyze defects of semiconductor devices in a nanometer range and basically investigate and solve defect causes in development of new processes and in mass production process.
An electron energy loss spectrum is broadly classified into a zero loss spectrum that does not lose energy when passing through a sample, a plasmon loss spectrum acquired by exciting a valence band electron and losing energy, and a core electron excitation loss spectrum acquired by exciting a core electron and losing energy. In the core electron excitation loss (core loss) spectrum, a fine structure is observed in the vicinity of the absorption edge. This structure is referred to as an energy loss near-edge structure (ELNES), and has information in which an electron state and a chemical-bonding state of a sample are reflected. Furthermore, an energy loss value (absorption edge position) is specific to an element; and therefore, qualitative analysis can be made. In addition, information related to peripheral coordination of an element of interest can be acquired from a shift of an energy loss value which is referred to as a chemical shift; and therefore, simple state analysis can also be made.
Conventionally, in the case where an electron energy loss spectrum at a different point on a sample is acquired, both a scanning transmission electron microscope in which a sample is scanned with a narrowly concentrated electron beam using a scanning coil and an electronic spectroscope which can spectrally decompose by an amount of energy in which the electron beam has are combined; and accordingly, the electron beam passed through the sample is spectrally decomposed and the electron energy loss spectrum is continuously acquired.
However, in the case of such a technique, the aberration and the position of origin of the electron energy loss spectrum are changed by a drift in accelerating voltage of the electron beam and a change in magnetic field and electric field due to a disturbance change in device periphery; and therefore, it is difficult to compare shapes of the energy loss near-edge structure or minimal chemical shifts, in the electron energy loss spectra for measurement positions.
In a usual transmission electron microscope, focal point positions in an x axis and a y axis are set on the same surface and a transmission electron microscope image is acquired; whereas, Japanese Patent Application Laid-Open (JP-A) No. H10-302700 (patent document 1) discloses that a focal point position of the x axis is set to a spectral surface and the other focal point position of the y axis is set to an image surface by making the focal point positions different in the x axis and the y axis in order to solve the aforementioned problem.
As a result, the electron energy loss spectrum in the y axis direction of a sample can be separated and observed. That is, as shown in FIG. 3B, an image acquired by an image detector can be observed such that the x axis is an amount of energy loss and the y axis is a spectral image having position information of the sample. The spectral image is observed in a belt-like shape in response to each laminated film observed in the transmission electron microscope image shown in FIG. 3A. Consequently, there can be observed the electron energy loss spectra at different positions of the sample at the same time, and it is possible to compare in detail energy loss near-edge structures or minimal chemical shifts, in the electron energy loss spectra for the different positions.
The spectral image having an amount of energy loss in the x axis and sample position information in the y axis is a two-dimensional image which is acquired by the image detector by changing lens action of the electronic spectroscope or the like, and by making the focal point positions different in the x axis and the y axis. The width in the y axis direction of the spectral image can be freely adjusted by changing the focal point positions in the x axis and the y axis; however, an observation magnification in the y axis direction in the spectral image needs to be calculated because the observation magnification between the transmission electron microscope image and the spectral image is different.
It is possible to calculate the observation magnification of the spectral image from both a film thickness measured by the transmission electron microscope image and a belt-like width of the spectral image; however, in the case of a sample where a chemical shift is observed at a laminated film interface and the like, it is difficult to calculate a correct observation magnification of the spectral image because the laminated film interface blurs in the spectral image.
Furthermore, it is not possible to simultaneously observe the transmission electron microscope image and the spectral image acquired by matching the focal point positions in the x axis and the y axis. That is, in the spectral image, it is difficult to correctly associate a position in the y axis direction where the electron energy loss spectrum is acquired with one in the transmission electron microscope image.